Follow-up from "Add VulnerabilityStateTransition model"

The following discussion from !87957 (merged) should be addressed:

• @Quintasan started a discussion: (+3 comments)

  question to maintainer: If my Postgres foo is correct then I think that adding an index on (vulnerability_id, created_at DESC) would be beneficial here because:

  1. Indexes on foreign keys are mandatory
  2. We will most likely want to present the state transition from the latest one to the first one (ORDER BY created_at DESC)
  3. The same index would be used for queries like SELECT * FROM vulnerability_state_transitions WHERE vulnerability_in (1,2,3,...,n);

  That way we could drop index: true from the migration creating the table and would have one index left